The present invention relates to supplying electric current to resistance heaters for maintaining the temperature at a desired level in the bladder of a water bed.
In the design and manufacture of waterbeds, it has been found desirable to enclose the water filled bladder in a casing for added user comfort. Water bed mattresses of this type have come to be referred to as "soft side" mattresses because of the several inches of foam material provided in the casing along the sides of the mattress. In this type of mattress a foam casing provides a secondary water containment in the event of a leak in the bladder. The foam casing must therefor be sufficiently wide to provide the stiffness necessary to maintain the containment if the bladder is ruptured and water fills the casing.
In the aforesaid soft side type waterbed mattress assemblies, it has been found convenient to provide the heater element for the bladder under the bladder and dispose the controller between the side of the bladder and the foam material forming the sides of the casing. In this type of arrangement, the controller is thus disposed with its side faces in a generally vertical orientation.
In soft side waterbed mattresses where the controller for the water bladder heater is disposed with the faces thereof in a vertical arrangement, it has been found that the heat generated by arcing of the contacts during switching of the current load for the heater has affected the temperature sensing element employed in the controller, thus causing the switch actuator to cycle power to the heater at false temperature settings with respect to the temperature of the water in the bladder. This has been found particularly troublesome where the switching mechanism employed bimetal temperature sensitive components.
It has thus been desired to find a way or means of providing a thermostatic controller for a soft side waterbed mattress which can be disposed vertically between the sides of the water bladder and a foam casing and yet one which will not be affected by the heat generated from the contacts switching current for the heater.